/Engine/Source/Runtime/GeometryCore/Public/Spatial/BlockedLayout3.h
the 3-d coordinates of the block specified by an index in a linearization of the blocks. BlockIJK is the lattice address of the block in terms of block units ( e.g. the location in a grid of blocks).
[FVector3i](API\Runtime\GeometryCore\FVector3i) BlockIndexToBlockIJK ( const int32 BlockIndex ) const